TDMA communications systems such as used in mobile ad-hoc networks (MANET's) are becoming increasingly popular. When TDMA is used with a MANET the network operates as self-configuring networks of mobile routers or associated hosts connected by wireless links to form an arbitrary topology. The routers, such as wireless mobile units, can move randomly and organize themselves arbitrarily as nodes in a network, similar to a packet radio network. The individual units require minimum configuration and their quick deployment can make ad-hoc networks suitable for emergency situations. For example, many MANET's are designed for military systems such as the JTRS (Joint Tactical Radio System) and other similar peer-to-peer or independent Basic Service Set Systems (IBSS).
A mobile ad-hoc network, with no fixed infrastructure, has also posed many challenges to the media access control (MAC) layer for multiple users. In a TDMA based ad-hoc network, it is sometimes difficult to assign non-interfering time slots to nodes and still allow spatial reuse of the bandwidth and time slots. Different nodes that are separated far enough would be able to reuse the bandwidth by using the same time slot.
A Carrier Sense Multiple Access (CSMA) based MAC design for an ad-hoc network is sometimes suitable for data transmission between mobile nodes. For example, 802.11 standards do not support voice or multimedia traffic with a desired quality of service because the transmission is contention based and asynchronous. The sharing of a radio resource often becomes unpredictable. To support voice and video streams, the system often requires bandwidth to be reserved. This could be accomplished in some TDMA based schemes by using non-interfering time slots, for example, channel scheduling.
A Code Division Multiple Access (CDMA) based system is bandwidth efficient in traditional cellular networks but it relies on adequate power control, maintained by the base station, for eliminating the near/far effect. In a mobile ad-hoc network environments, however, CDMA technology has encountered some difficulties.
The TDMA communications systems are more preferred and use a channel access system for shared radio networks. The signal is divided into different timeslots allowing users to share the same frequency channel. Users can transmit one after the other using their own timeslot within a frame (or epoch). Thus, multiple stations can share the same transmission medium or radio frequency channel and use only part of the bandwidth. A data stream in this type of system is divided into a frame (or epoch), which is divided into timeslots. Each user is allocated one timeslot, which could contain data and a guard period for synchronization.
There are issues as noted before with the network size and the media access control (MAC) configuration. The TDMA frame (epoch) and slot format are hard to configure to a fixed format while serving the purpose for networks having different sizes. In a TDMA communications system, a matching network size configuration is required to enable successful communications between users corresponding to the network nodes. In some TDMA systems, a waveform, for example, an advanced networking wideband TDMA waveform (ANW2) is used with different radios having an extended range and operating in accordance with the Software Communications Architecture (SCA).
It may be desirable to support many different network sizes, for example, a 2-node network for high capacity; a 10-node network for a high and low bandwidth mesh network; or a 48-node network for a high and low bandwidth network as non-limiting examples. Depending on the number of nodes, the epoch (frame) is divided into specific timeslots. For example, with two nodes the epoch (frame) may be divided into two timeslots. With four nodes the epoch may be divided into four timeslots and with eight nodes there are a corresponding eight timeslots. Problems can develop when one radio or other communications device attempts to enter a network and its communication with a different network configuration. For example, a node that tries to enter one network having four nodes and four timeslots, but is configured for only two nodes, would not be able to communicate with the nodes configured for a 4-node network. Current techniques to solve this problem allow the system to configure manually all nodes to the same network size, which can be time-consuming, or use some other communication system to confirm a configuration. This can be inefficient.